Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.


Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Donate

Twitter Facebook YouTube Pinterest

RSS Posts RSS Comments Email Subscribe

Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...

Keep me logged in
New? Register here
Forgot your password?

Latest Posts


Climate Hustle

Websites for Watching the Arctic Sea Ice Melt

Posted on 8 June 2011 by michael sweet

The Arctic Sea Ice collapse is one of the most obvious changes caused by Global Warming.  Last winter's minimum was the third-lowest ever recorded.  The rapid melt of the sea ice has led to scientific predictions of an ice-free Arctic Ocean in summer as early as 2013 (though most mainstream predictions range from 2030 to 2050). Every northern hemisphere summer, some bloggers watch the ice melt and try to guess what will happen.  Others claim it is like watching paint dry.  I think the situation is similar to watching a season of sport.  The individual games are interesting to watch, and difficult to predict, but the final season record is what really matters.  This article will give some web sites to check if you want to be informed about what is happening this season, but do not want to follow the day to day action.  I posted a similar thread with links to more websites last year on Skeptical Science.

My favorite place to find out what is really happening in the Arctic is the National Snow and Ice Data Center (NSIDC) web site.  This site has a sea ice extent graph that is updated daily.


It compares the ice to 2007 (the record low year) and also to the average from 1979 through 2000.  The sea ice extent is defined as the area of ocean that is covered by at least 15% sea ice.  In addition they have a very nice FAQ section that answers many sea ice questions.  This FAQ section is a good place to find out the basics in one place that you can trust.  NSIDC has a monthly commentary on the sea ice conditions.  It is usually issued around the fifth of the month.  This commentary discusses current sea ice conditions, relevant weather and whatever else the scientists at NSIDC think fits the situation.  If you read only the NSIDC summary every month you will be well informed about the sea ice this summer.  NSIDC also issues reports when something special happens, like if a new record low is set.  These comments happen less often.  Hopefully they will expand their commentary this summer.

Cryosphere Today is a good site to look at data.  They offer no commentary on the data.  They have a daily graph of the sea ice (from the University of Bremen) to follow the daily action. 

 They have a graph of the sea ice area from the past two years that gives you an idea of what has been happening for the entire melt season. 

The sea ice area is defined as the total area of the ocean covered by ice.  They take the sea ice extent and subtract the open ocean portions.  There is a little more error in the sea ice area than the sea ice extent; that is why NSIDC and IJIS use the sea ice extent.  In general, it is best to compare one site's graphs with their own graphs.  Cryosphere Today has about 10 local area maps that are interesting. 

They also have a comparison app that allows you to compare any two days of ice in the satellite record. 


Notice above how much more ice there was in 1980.  The snow data is only present for the past few years.

Cryosphere Today also has data from the Antarctic.

IJIS has a good site to check on the sea ice extent on a daily basis.  Their graph is similar to the NSIDC graph, but they include all the years from 2002 to the present (they do not show the long term average).  You can quickly compare the current extent to previous years.  

AMSR-E Sea Ice Extent

Lately 2011 has been running near the record low.

If you check these sites occasionally and read Skeptical Science posts on sea ice during the summer, you will be able to keep up with what is going on.  If you are interested in learning more about sea ice, Nevin’s Arctic Sea Ice Blog is a good place to read.  Amateurs test their predictive powers against the ice.  Nevin has a very complete daily graphs page which includes much more data than I have described here.  If you want to watch the daily struggle of the ice against warming, this is the place to go.  Nevin has links to all of the arctic web sites that I visit.  Please attach links in the comments to other interesting sites. 

If you want to keep up with the "skeptics", WUWT and Steve Goddard have a lot of commentaries on sea ice.   Somehow they can look are a new record low and tell you the ice is recovering.

Any discussion of skeptics and sea ice would be incomplete without this graph from Denial Depot:


This graph is a little dated, but great skeptic data can be reused forever.

Have a good time following the Arctic Ice this summer.


Regular Skeptical Science contributor Sphaerica has kindly made available the following graphics, which add clarity to the discussion:


Note that the areas of increased melt indicated by the yellow boxes are all at lower latitudes around the edges (warmer temps, warmer water).

0 0

Bookmark and Share Printable Version  |  Link to this page


Prev  1  2  3  4  5  Next

Comments 51 to 100 out of 208:

  1. Dorlomin
    FWIW there are two trends that have strongly influenced the rate of sea ice melting in the NH, there is additional warm water moving into the area and the winds have been more in favour of exporting ice out of the arctic. A change in either of these may see the rate of decline slow or even briefly reverse the trend.

    Much appreciated, I’ve been looking for the reasons for these blips for a while .Thats the first sensible answer I’ve seen. Incidentally one of the things I have noticed ( entirely subjective of course) is that when it is unusually cold here in the North East Atlantic, it tends to be unusually warm in the Arctic. I suspect the influence of a melting Arctic is being felt in Europe in counterintuitive ways. These synoptic charts could be useful in looking at this process.
    0 0
  2. Garethman at 50:
    Does WUWT have a graphs page comparable to Nevin's daily graphs page(linked in the main article and also in the comments)? Can you provide a link to the WUWT page so we can check it out?

    When you say "unusually cold" do you mean compared to the past 20 years or compared to say 1900-1930?
    0 0
  3. Garethman - the observation about favourable winds is in the literature, particularly for 2007's melt. But the winds are overprinted on the declining trend, such that, although winds in the latter half of the melting season last year (2010) were extremely unfavourable to ice export, the ice was so thin that it melted to the 3rd lowest extent on record. Heaven knows what'll happen to the remains of the Arctic ice when we get a repeat of 2007-like wind conditions (IIRC, it was about a 10-year return period for that wind pattern).
    0 0
  4. 'Notice above how much more ice there was in 1980. The snow data is only present for the past few years.'

    I keep looking and keep not seeing it - it looks like there is more ice at present? I looked up the comparison again and it looks the same there; perhaps the answer is that the 2011 image displays sea + land ice whereas the 1980 image only displays sea ice? The website writes: 'Historic snow cover data not displayed on these images. ... Snow cover data is displayed only for most recent dates.'
    0 0
  5. 54, Chuckbot,

    Not sure what you're looking at. Here's the most recent view, with the differences focused by the yellow boxes.

    You'll note that the areas of increased melt are all at lower latitudes around the edges (warmer temps, warmer water).

    Honestly, at the moment, in my opinion, this year is clearly shaping up to be the worst on record. It could turn on a dime, but right now, my opinion is that without an abrupt stall (as happened last year) we're actually in for the new record low.

    (I also skipped the area of the Nares Strait, at the upper left corner of Greenland from this perspective. It's not as obvious, but in 2011 you see an empty patch in the strait itself, with green/sparse ice, while in 1980 you see a very small empty patch surrounded by more higher ice concentrations).

    If you go to Cryosphere Today to see the more detailed image, you can see it better, as well as seeing how much further advanced the melt is just a few days later than the 6/9 images here.
    0 0
  6. Thanks - I think I am getting distracted by the snowfall; the rectangles highlighting the differences help a lot.
    0 0
  7. Oh. Snowfall didn't exist on the images in 1980, which is probably why that looks like there is none... it's there, just not in the pictures, so its impossible to compare. I don't know when they started to track it on these pics (they only say "most recent dates"). But if you go to Cryosphere Today and do your own comparisons with more recent years, you'll also see that the snow cover is greatly reduced this year, and was in fact one of the first signs of things being worse this year, back when it was still too early in the season for sea ice concentrations to vary by much.

    To look at snow cover as well as snow anomalies, and over the entire northern hemisphere, try The Global Snow Lab (Rutgers University). Just follow the links. There are lots of cool tools. In particular, look at the anomalies for March (i.e. the consistent onset of earlier spring melt due to climate change).
    0 0
  8. michael sweet,

    You should probably amend your text with the image, to highlight the point of chuckbot's confusion. I imagine many people will find their eyes drawn naturally to the white snow as the comparative indicator, not realizing that it's the red/purple sea ice concentrations that are the focus, or that the 1980 image simply lacked representations of snow cover.
    0 0
  9. garethman,
    The temperature difference between the Arctic and NE Atlantic do tend to move in opposite directions based on the AO (Arctic oscillation). During the positive phase, lower Arctic pressure results in stronger winds over the Arctic, keeping colder weather bottled up in the Arctic region. During the negative phase (the past two winters), higher pressure exists in the Arctic, with lower pressure in the mid liattitudes, allowing the cold Arctic air to migrate southward. Storm tracks also tend to follow the winds southward, resulting in more snowfall.
    With colder waters in the North Atlantic, I suspect sea ice will not surpass the 2007 lows. Even though the current expanse is low and smiilar to 2010, the rate of decline is less (2010 had a larger April extent). It may come down to the winds and current again. I do not read too much into one year anyway, but rather the longer term trend.,-June-13,-2011
    0 0
  10. 59, Eric the Red,

    Doesn't it strike you as a little odd that in every single aspect of climate change you are able to look on the bright side, and rationalize a way in which rising temperatures can't possibly exist at all? The Arctic is melting at a frightening rate, and you "suspect sea ice will not surpass the 2007 lows," and anyway it's all due to wind and currents, and anyway another record low in an ongoing stream of record lows is no big deal anyway because you need a trend -- meaning a lot more years to watch the record lows keep one upping each other.

    Really, I'm sorry, but if this happened once or twice it would be credible. When someone can't admit to any symptom of a warming world, it's beginning to look like... shoot, I can't think of a good, acceptable word to use. Do you have any clearly rational, positive-sounding suggestions?
    0 0
  11. 59, Eric the Red,
    I do not read too much into one year anyway, but rather the longer term trend.
    Then you must be scared to death, and ready to take serious action on climate change, because ignoring any particular year, and looking only at the trend... that trend is frighteningly obvious in its implications.

    0 0
  12. Sphaerica,
    Not sure what you mean. When have I ever said that temperatures were not rising?
    If you restrict your observations to record lows and highs, you may be missing the bigger picture.
    Are you implying that the influx of warm Atlantic waters does not impact Arctic sea ice? It sure sounds like it from your previous posts.
    I stand by my prediction that 2011 will not surpass the 2007 low. In fact, since sea ice is falling at a lower pace than last year, I suspect 2011 will not surpass 2010. If you believe that it will, please explain why.
    0 0
  13. Sphaerica,
    Your illustration with the boxes is really nice. Hopefully people will see it in the comments if they have trouble seeing the difference in the main post. I think it is too late to change the post now.
    0 0

    [DB] It can be done via an Addendum at the end.  If you wish, I can do it for you.

  14. DB: that would be nice. Sphaerica's illustration is better than mine.
    0 0

    [DB] Done.

  15. PIOMAS (see link in #33 above) has released an update through the end of May based on a revised model and a new baseline (1979 - 2010 average). The new model is showing a less severe declining trend, but the minimum is still ~4000 km^3 ice last September. That would seem to imply that some of the older values have been reduced such that the overall trend is lower while still arriving at the same end result. There are also some new materials like a graph showing the baseline values compared to 2007 and the current year. There are new links to validation information and the values used for the anomaly graphs, but the links on the PSC page currently have some '-2' extensions which I had to manually remove to find the intended pages.

    Also, there is apparently going to be an announcement about Cryosat-2 data next week. Sounds like they are going to start releasing results.
    0 0

    [DB] Thanks for pointing that out.  I was going to post this last night but my PC died:


    The new graphics more clearly depict the 2-sigma bounds.

  16. DB:
    Neven's name is spelled wrong twice in the last paragraph, can you change to Neven from Nevin?

    Please delete this post.
    0 0
  17. Can anyone explain why the Artic always seems to consistently have such a high temperature anomaly in the world maps, more so than anywhere else? Or maybe there's an article in SkS that explains why?
    0 0
  18. BC
    it is known as polar amplification. You may want to start with this post at RealClimate.
    0 0

    [DB] And also this post here at SkS:

  19. 33,35,65... Cryosat-2 just around the corner!

    I share your excitement - not least because I used to work with some of the team on envisat... evil bastards, working to become millionaris using this stuff to take over the world via the UN on the back of the scam known as AGW great scientists, thrilled for them.
    0 0
  20. As a side note, melt pools first appeared this year on North Pole Web Cam 1 on 6/19 about a week ahead of last year (6/25).
    0 0
  21. Heh... was just on my way here to post that map les. Also an article on it here.

    The map you included above seems to show that the really thick sea ice (5 to 10 meters) which used to cover a large portion of the Arctic ocean is essentially gone (just a few scattered dots of 5 meter ice) and most of the remainder is 3 meters or less. This doesn't seem radically different from past estimates so I suspect the PIOMAS volume values have been in the right ballpark.

    The article above also has an interesting ice thickness graphic for Antarctica.

    Looks like they are going to start their data record from January 2011. They launched in April 2010, but presumably they don't want to use data from the calibration and early validation period so 1/1/11 is a good start point. They've been validating the satellite readings against plane and ground measurements and have completed that through February. Will likely continue validation for several more months before releasing satellite results without extensive cross-checking.
    0 0
  22. Nice graphic.

    The melt pool may not be significant as the sea ice extent is essential the same as last year.
    0 0
    Moderator Response: (DB) The volume is what matters; by melt season's end, 2007 will fall.
  23. Eric, extent isn't a particularly useful metric except for determining trends over a long time period. As DB notes, volume is the defining factor... though unfortunately much more difficult to measure.

    Extent = area / average concentration

    From this simple formula it is clear that extent is as much determined by how spread out the ice is as by the amount of ice surface... and it completely ignores how thick it is (and thus how much energy is required to melt)

    Volume = area * average thickness

    Comparing this formula to that for extent we can see that extent is essentially a proxy for volume with two potential error factors (no thickness component and variable concentration).

    The lowest extent was in 2007 and at the time that was also the lowest volume, but volume in 2010 was significantly lower and thus far volume this year has been lower than 2010. With the two 'error factors' it is still possible that the 2007 extent will not be broken, but as the volume continues to drop it becomes less and less likely.
    0 0
  24. That is a strong statement. Do you have any evidence to support it?
    0 0

    [DB] "I shall be telling this with a sigh
    Somewhere ages and ages hence:
    Two roads diverged in a wood, and I,
    I took the one less traveled by,
    And that has made all the difference."



  25. according to PIOMAS, sea ice volume has been below 2007 values for the past two years.
    0 0

    [DB] FYI, that is a hindcast product (PIOMAS 1), with quadratic curves fitted to them.  I.e., not to be taken as a prediction for future performance.  The graph I posted above is from the newer system, PIOMAS 2.  Less volume = less area and extent.

  26. Eric,
    "The melt pool may not be significant as the sea ice extent is essential the same as last year". Last year was the lowest ever recorded. The melt pools this year appeared at the North Pole a full week before they have ever been measured before.

    Do you realize that the IJIS area for 2011 has been the record low of all time for the past week? It has crawled above 2010 and is now just second lowest. You appear to be arguing that since it has not set a season record minimum yet (the melt season is only beginning) that there is no problem. What would constitute a problem if being at the lowest level ever recorded for the current date is not a problem??
    0 0
  27. michael,

    last year was the third lowest recorded (2007 was the lowest, followed by 2008).

    We are approaching the halfway point in the melt season, and a time when the rate of melting reaches its maximum. 2007 was near the high side of the past 10 years during mid June, but went into a steep decline thereafter. Clearly this date is nothing special in the measurement season. In fact, going back one month, to the middle of May, and 2006 and 2004 had the lowest sea ice extent, yet neither of those years made the bottom five.

    Today's date is irrelevant. Wait until Septemeber, then we will see.
    0 0
  28. Given that ice 'extent' can vary by as much as 667% (1 / 0.15 minimum concentration) for a given ice 'area' I'd agree that "today's date is irrelevant"... but so is any given September minimum. Ice extent is simply too disconnected from ice amount (i.e. volume) for any single year value to be significant.

    Right now ice melt pond formation, extent, area, and total volume are all at new record values... which certainly makes a new record minimum extent this year seem more likely. However, given the huge potential disconnect between ice amount and ice extent anything could happen.
    0 0
  29. I would say that a given minimum or maximum is more telling than the ice at a particular date. But I agree that a single year should not be given too much attention or taken out of context of the larger trend.

    Yes, anything could happen.
    0 0

    [DB] "Yes, anything could happen."

    Yes, anything physics-based.  Which (at this point) eliminates a recovery of the ice to pre-1980 conditions.

  30. Eric,
    I know that 2007 was the lowest year at the end of the melt season. The problem is you are mixing up different measurements. You said "The melt pool may not be significant as the sea ice extent is essential the same as last year". This clearly is talking about the current sea ice extent, not the end of summer extent. Obviously you cannot tell what the end of this year will be since it has not happened yet.

    As CBD said, "Right now ice melt pond formation, extent, area, and total volume are all at new record values... ". If that is not a problem for you than that is how you feel. But to claim that the ice has somehow recovered is not true.
    0 0
  31. michael,

    Of course no one knows what the end of summer sea ice extent will be. That is the point.

    Currently (June 22), the sea ice extent is similar to 2010, and much lower than 2007. Yet, 2007 turned out to be much lower than 2010. Thus, the sea ice today is not necessarily relevant to what will happen in September.

    Do you understand now?
    0 0

    [DB] Why the fascination with extent when volume is the better metric?  That's like focusing on HadCru data for Arctic temps when GISS is by far the better metric.  Extent is not really relevant except for albedo flip & Arctic heat budget.

  32. 81, Eric the Red,

    And what exactly would yet another record low (which would be the 6th such record in the past 20 years, meaning that each subsequent record broke the previous records) mean as far as a trend?

    At what point would a truly skeptical person start to say "whoa, what's going on here?"

    You think the trend is important. What is the trend in sea ice extent? What is the trend in your own repeatedly demonstrated belief system? At what point, on what issue, are you going to start demonstrating anything other than blatant denial?

    Do you understand now?
    0 0
  33. To what denial are you referring?

    That is exactly the trend to which I am referring. 2007 was anomalously low, just like 1996 was anomalously high. Other than that, the trend looks robust. I do not know why so many people are getting exciting about breaking the 2007 low this year.

    I have always understood.
    0 0
  34. Tamino has now weighed-in on the ongoing Death Spiral in the Arctic:

    Sayonara, white lumpy rain.
    0 0
  35. Eric wrote: "I do not know why so many people are getting exciting about breaking the 2007 low this year."

    I haven't noticed this 'excitement', but 'Arctic sea ice has been recovering since 2007' is a frequently repeated denier falsehood... so the next new record breaking year (in sea ice extent or any other cherry-picked factor) is always welcome as proof of the ridiculousness of that argument. Though in this case the continuing decline in Arctic sea ice volume already provides more than enough proof.

    What is particularly interesting about this year is that the trend in ice volume decline has reached the point where it either has to level out or hit zero in just a few years. If the volume drops as much from 2011-2014 as it did over the 2007-2010 period then we are looking at an essentially ice-free Arctic ocean. It isn't certain that this year will be determinative, but it could be and we'll definitely know one way or the other by 2015.
    0 0
  36. Eric the Red @83, I am definitely getting excited about low ice, and not because it is a good thing. It just happens that the deniers are winning the PR war and as a result humans will probably not do anything adequate about it till it is too late. But one thing, I am sure, will cut through all the lies, obfustications and misdirections of the deniers - when a commercial ship sales from the Atlantic to the Pacific across the North Pole and sees no ice, the deniers game will be up.

    Unfortunately that will probably not be till 2030, and the used by date for effective action closes in 2020.
    0 0
  37. Tom,
    I am not of the belief that there is an expiration date for action. Most effects appear to be reversible - action will just become harder.
    0 0
  38. Eric, the longer you delay the more expensive action becomes. At present effective action will cost between -1 and 3% of global GDP. If you wait five years that will shift downwards. If you wait ten years it will shift further down, and you will need to undertake geo-engineering to bring CO2 levels below 450 ppm and to keep temperatures down while you do it. At that rate it does not take long before costs exceed 5% of GDP, ie, the World will have a significant negative net economic growth which will be needed to be sustained for decades. That is another way of saying it just won't happen and we will bear the brunt of even greater overall costs because some people are fortunate enough to avoid them.
    0 0
  39. Eric:
    Please provide citations for your outrageous claim that 'Most effects appear to be reversible ". Comments made without evidence can be dismissed without evidence.
    0 0
  40. michael,

    What effects are not reversible? This comment is neither outrageous nor demanding of evidence.


    Yes, it will become harder. Just like waiting to save for retirement.
    0 0
  41. If we stopped emitting CO2 today the temperature would continue to increase for decades because of the heating in the pipeline. It is prohibitively expensive to remove the CO2 and pump it under ground. The temperature effects already measured are enough to raise sea level several meters . This will flood Florida and Bangladesh, in addition to many huge cities. In the past year China, Russia, Australia, the USA and the Amazon have had record damaging weather. How will these effects be reversed, since it will not get cooler? You have presented only your unsupported opinion so far. How will the effects of the permanent pollution that has been put in the atmosphere be reversed??? Provide data and references to support your extraordinary claim. Comments made without evidence can be dismissed without evidence. I dismiss your claim without evidence.

    We need to take immediate action to keep things from getting worse. The longer we wait the worse it will become. The uninformed opinion that things will reverse in the future, for no apparent reason, does not help motivate people to take action.
    0 0
  42. Several meters, wow! And you thought my post was outrageous. I guess I can dismiss that one.

    CO2 will not stay in the atmosphere forever. If we were to stop emitting today, the level would fall slowly. The longer we wait, the longer it will take (I presume that is your get worse statement).

    You have not given me any reason to think that this is not reversible.
    0 0

    [DB] If we cease all human CO2 emissions all hold them at zero ad infinitum, then CO2 levels would first begin to flatten their rise and then plateau on the decadal level.  The natural sinks would begin their slow draw-down on the centannial& millennial timescales.  All the while the system will be changing to reach a new thermal equilibria & temps will continue to rise...and ice will continue to melt.  For centuries and millennia (repeat as needed).  The loss of the WAIS and the GIS, which is in store before equilibria can be reached, is not reversible except on the hundreds-of-millennia to millions-of-years timescales.  Unless you're a Timelord like Dr. Who...

    You really are not doing well in retaining credibility here with your unscientific opinions.  Perhaps a change in venue is needed, where said opinions will be more welcome & reflective of the caliber of the Forum in which they're posted?

  43. Eric, reversing effects?

    It's a simple question. Just how many mountains (of suitable rock composition) are you prepared to blow up? Every year?

    Each year's CO2 production from oil alone equates to 93 million years of CO2 sequestration in those fossils. Unsurprisingly, natural geological sequestration is entirely unable to keep up with the release.

    If we want to "reverse" the many impacts of our accelerated geological CO2 releases, we'd better pay some attention to accelerating geological CO2 sequestration. That is, expose the maximum area of rock surfaces to air and water. Blow it up, reduce it to gravels and dust. Move on to the next one. If we can do it for coal, we can do it to counteract coal.

    I know many people believe we can do it with biological sequestration alone. We could do it that way. If we could ensure nil deforestation as well as universal adoption of soil carbon retaining practices, it could be done. I have no confidence that anyone or anything on earth will ever restrain the logging companies in the Pacific region, let alone worldwide.

    So. How many mountains per year?
    0 0
  44. Comments made without evidence can be dismissed without evidence. I have provided data to support my position. You have not. Until you provide data to support your position you are dismissed.

    Eric the Red is a (-Snip-) who should be banned since he refuses to provide data to support his positions and refuses to even read data provided to him that shows he is wrong.
    0 0

    [DB] Fixed html tag and snipped a bad-sounding word.

  45. Reversing processes is not necessarily simple and linear - if the system exhibits hysteresis. An example is an ice sheet, whose height above sea level (and thus lateral extent) begins to decrease. This places a smaller area of the ice sheet above the snowline, encouraging subsequent decrease in snow accumulation. Continue this process and you can lose an ice sheet without continued warming.

    The height of the exposed land surface is now much lower than the surface of the original ice sheet. How do you make the snow hang around through the summer in such a way as to regrow the ice sheet?

    It's a bit more complicated than that (flow dynamics and precipitation changes complicate the picture somewhat), but this is what is at stake with both the Greenland and W Antarctic ice sheets. That's many metres of sea level.

    So. How do you grow back your ice sheet, Eric?

    On the thread topic, dark water absorbs more energy than white ice. More dark water surrounding the remains of a melting sea ice cap absorbs more energy and does not freeze quite as easily (and certainly not to the same thickness). Once the Arctic ice is gone... how do you grow back the reflective ice cap that is one key to current global temperatures, sea level (through cooling the GIS) and weather patterns?

    These things may be reversible (though you provide no evidence as to why), but certainly not in the short term once the hysteresis takes hold...
    0 0
  46. Since the volume of ice in Greenland is ~2.8 million cubic km, and the maximum current rate of loss is ~100 cubic km / year, that is many millenia before Greenland will melt. The IPCC predicted that it would take a 5.5C temperature rise to melt Greenland, and it would take several centuries. Recent studies show that the melt rate is significantly less.
    0 0
  47. Sky,

    If Greenland were to melt completely, it would take another ice age to regrow based on the altitiude of the current glacier. Based on previous evidence, this is unlikely to occur anyway.

    Sea ice can regenerate every year. Sea ice is governed by water temperature. It is reversible. Current trends show that the Arctic could be ice free in summer by 2050, however, winter sea ice is likely to remain for many centuries.

    0 0
  48. Eric: You have presented data at last!!
    You have found an interesting article on Greenland. They model that the ice melt on Greenland will peak and then decrease as the temeprature increases. Melt last year was greater than they project for the coming, hotter decades. Hansen (linked above) projects that the melt will double every ten years. For the past 8 years the satelite data shows that melt has increased at a faster rate than Hansen expected. Perhaps your model will proove correct and the melt will slow down in the future, it will be interesting to see how this paper is received by the scientific community (it is too new to know how it will be received). Hansen made his projection several years ago and most people seem to think he is high, but the data support him so far.

    For sea ice you have also picked the longest projections for an ice free arctic. Maslink, linked above, projects an ice free Arctic as early as 2013. We will see in a few years, perhaps ths September, who is more correct.

    You always choose the most optimistic projections to base your choices on. Do you realize the risk associated with that course?

    You have not addressed my comments on flooding (20,000,000 people lost their homes in Pakistan alone, not to mention China, Australia and the USA), drought (largely responsible for the fires sweping the USA right now, Australia had it's share this year) or ocean acidification (which I did not mention before but is a severe effect that must be reversed).

    Which of these effects are reversible? How will they be reversed? Please provide more data, since you have shown the ability to find some.
    0 0
  49. Eric, from your own linked article about Greenland: "Richard Alley of Pennsylvania State University cautions that Price’s model does not provide an upper limit to sea level rise." Additionally, while I do not of course expect Greenland to disappear within my lifetime, the point is that we are setting up a chain of events that will not just reverse with a slight decrease in CO2.

    As for sea ice, try this discussion of sea ice volume. Do you think trends in Arctic sea ice are or are not showing accelerating declines. When does the acceleration show most clearly - when ice is thickest, or when ice is thinnest? Do you think you can put a straight line through data points (with no mechanical/physical reason why) and say that this will be the trend in the future?

    It would be nice to have your optimism, but real physical systems do not operate in the simplistic way you would like them to behave.
    0 0
  50. All,

    My comments were to counter michael's claims that if we stopped emitting CO2 today that temperatures would continue to rise dramatically, resulting in several meters of sea level rise.

    My point was that nothing that has happened to date is irreversible. No one has presented anything to dispute that contention. Speculating that future events will happen does not constitute evidence.

    What is the best way to predict the future? Simple, by looking into the past. Some may call this optimistic, becasue I am not anticipating acceleration in the trends. Can you actually say something is accelerating based on one or two points? Do you reason to believe that the trend is nonlinear?
    0 0

Prev  1  2  3  4  5  Next

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

The Consensus Project Website


(free to republish)

© Copyright 2019 John Cook
Home | Links | Translations | About Us | Privacy | Contact Us